The present invention is broadly concerned with an improved slotter head assembly of the type used in box-making equipment for forming flap-defining slots in box blanks. More particularly, it is concerned with such a slotter head assembly which is improved by provision of a uniquely shaped, pressurized, fluid-actuated bladder mechanism which is received by and cooperates with a head recess having an internal surface cross-sectional shape closely resembling that of the outer bladder surface. The improved bladder mechanism cooperates with the head assembly for selectively locking the slotter blade knives in position, while permitting ready adjustment of the knife positions. In this fashion, the box blank slotting equipment can be readily altered to produce blanks of different configurations without the need for time-consuming manual knife adjustments. In preferred forms, the pressurized, fluid-actuated mechanism includes an elongated, pneumatic bladder positioned adjacent the corresponding knife blades and operable upon pressurizing the bladder to engage and lock the knives in place.
The manufacture of box blanks on an industrial scale normally involves slotting and creasing of precut corrugated sections in order to create a blank having the requisite fold lines and flaps for a given box. Normally, the slotting equipment used for this purpose includes an elongated shaft carrying a plurality of annular, rotatable slotter heads. Normally, a pair of slotting knives are secured to each head for rotation therewith. The circumferential spacing of the slotter knives thus determines the depth of the flap-defining slots for a given blank.
A persistent problem in the box-making industry stems from -the time and effort required to change the position of slotting knives on the individual slotting heads. That is to say, after a given box blank run is completed, it is often necessary to change the circumferential location of the knives in order to produce in the next run blanks of different configuration. Generally speaking, prior art slotter heads are equipped with a series of threaded bores, in the sidewall thereof, for attachment of the slotted knives by means of bolts. When it is necessary to change the location of one or more of the knives, it is necessary to remove the knife-retaining bolts, relocate the knife to a desired position, and reinstall the bolts. This practice can be relatively time-consuming, especially when it is considered that a number of heads need to be changed for each run. Moreover, the slotter heads are located within large blank-forming equipment, and it is sometimes difficult to gain access to the heads for knife changeover.
U.S. Pat. No. 5,174,184 (incorporated by reference herein) describes a slotter head assembly having pneumatically-locked slotter blades especially designed to allow for quick knife adjustment without the need for removing and reinstalling bolts or other mechanical fasteners. In the '184 patent, quick knife adjustment of the knife assembly is provided by means of a head presenting a knife-receiving slot in the periphery thereof, with one or more knives being adjustably positioned within the slot. Structure is provided for releasably locking the knives within the slot, including a pressurized fluid-actuated bladder mechanism adjacent a slot for selectively engaging and locking the knives in place.
In the preferred form disclosed in the '184 patent, the head is in the form of an annular, rotatable body having an elongated slot in the periphery thereof, permitting placement of one or more knives at any one of a number of positions around the slot. The knife-locking mechanism advantageously includes structure defining a fluid-receiving cavity and means for permitting selective filling of the cavity with pressurized fluid and for selectively draining pressurized fluid therefrom. Filling the cavity creates a locking action on the knives, while fluid drainage releases the knives. One or more elongated, pneumatic bladders formed of resilient synthetic material are provided within the rotatable head and conventional valve means is coupled with each bladder to permit selective inflation thereof with pressurized air, or, alternatively, deflation thereof. One or more shiftable plates are provided adjacent the bladders and are moveable laterally to a limited degree in response to filling or draining of the bladders. The shiftable plates are oriented for engaging the knives so that, upon inflation of the appropriate bladders, the corresponding knives are rigidly locked in place along the knife-receiving slot of the head. When it is desired to change the knife position, it is only necessary to partially or completely deflate the corresponding bladders, whereupon the knives can be manually moved to the next position and re-locked by re-inflation of the bladders.
In experimental practice with the apparatus described in the '184 patent, it has been determined that the elongated, pneumatic bladders may initially undergo radial expansion into the bladder recess excess void spaces in locations non-adjacent to the shiftable plates before locking action is imposed on the knives. Under such circumstances, the result may be that undesirable higher fluid pressure in the bladder is necessary to effect knife-locking action. Higher pressures in the bladder is undesirable because it either leads to a higher incidence of bladder failure for a given material of construction or requires that bladders be fabricated from more costly materials.
Accordingly, there is a real and unsatisfied need in the art for a simplified slotter head and knife arrangement which incorporates a pneumatic bladder assembly that achieves knife-locking action with a lower fluid pressure.